Symptoms: Car will idle at 2200 rpm while moving down the road. If stopped the idle ticks down to 1700, then it will finally come down to 1000 rpm after about 10 seconds. When revving the engine up, the rpm's drop far too slowly. When depressing the clutch, usually the rpm's will shoot up about 200-300 then start their slow decent. The car is running great after a major tune up. This idle thing is starting to hang me up though.

I've replaced my IAC valve twice with no luck. I've replaced my TPS sensor just to check and no luck. I've gone through the idle learn procedure a few times. I do not believe I have a vacuum leak. I've checked brake booster lines and PCV valve lines and they are good, other lines I've looked at look good. I've sprayed starter fluid all over the intake and common vacuum lines without any noticeable change in idle speed.

When I disconnect the IAC valve the car runs great! Idle is around 800 rpm and the throttle response is good and the rpm's will drop right down to 800 rpm after letting up on the throttle.

I'm about to break down and go for a smoke test from a local garage. Any ideas before I sink more $$ into this project?

Do autozone "cheaper" IAC valves just suck that badly that they don't work properly?

I have the exact same problem but it only began once I had it tuned- i used Tom (most people on here do) and an Excalibur 2 tuner. I tried to troubleshoot this with him but we never fixed it. I chocked it up to being a peril of remote tuning and figured I'd dyno it if I really wanted to fix it.

Please let me know what the issue was when you solve it... I'd be most interested to know.

You have a vacuum leak. Being the cars that old I'd venture it's either the intake gasket or an injector oring.
as for the problem since getting a tune, check to make sure your tb butterfly isn't closing all the way. should have about 1/8" gap (may have to play with the adjustment to find what the car likes, trial and error). otherwise it will set itself to high idle using the iac.

check to make sure your tb butterfly isn't closing all the way. should have about 1/8" gap (may have to play with the adjustment to find what the car likes, trial and error)

I believe my throttle body butterfly is completely closed. I was under the assumption this was normal and the idle is completely regulated by the IAC valve. You're saying I should adjust the idle screw until there is a bit of a gap (1/8th inch)? I have no idea what the previous owners have done to the car, but you're saying if the butterfly is completely closed it will force the ECU to run in a "high idle mode" to compensate for the closed butterfly? This might make some sense because again, with the IAC valve disconnected the car revs and idles normally.

Is there any documentation available on adjusting the TB butterfly?

Also, if an injector o-ring was leaking, wouldn't there be a hint of gas smell in the engine compartment. I have not detected the faintest hint of a gas smell while working on the engine.

One thing I've noticed is the engine idle and rpm behaves exactly the same if the car is cold or normal running temperature. This lead me to test the thermostat...

So I put the car into diagnostic mode on lunch today and the engine temp never climbs above 130F!!!. The upper coolant hose is always warm and you can feel the water flowing. Its been hovering around 32F outside, the radiator fans never kick in and the radiator is cold to the touch.

The heater gets warm, warm enough to properly warm the car, but its not piping hot either now that I think about it.

For what its worth I did have a bad iac valve. The replacement brought the revs down but the failed thermostat is keeping the engine in warm up mode. Gas mileage has also been terrible confirming the stuck open thermostat.

sorry, I should have made it clearer that was meant for eklipse who started having the idle problem after loading a tune.

Quote:

Originally Posted by rycodge

I believe my throttle body butterfly is completely closed. I was under the assumption this was normal and the idle is completely regulated by the IAC valve. You're saying I should adjust the idle screw until there is a bit of a gap (1/8th inch)? I have no idea what the previous owners have done to the car, but you're saying if the butterfly is completely closed it will force the ECU to run in a "high idle mode" to compensate for the closed butterfly? This might make some sense because again, with the IAC valve disconnected the car revs and idles normally.

Is there any documentation available on adjusting the TB butterfly?

Also, if an injector o-ring was leaking, wouldn't there be a hint of gas smell in the engine compartment. I have not detected the faintest hint of a gas smell while working on the engine.

I replaced my thermostat and it appears my original thermostat was working correctly. Car exhibited the same symptoms (low temp readings from the CHT sensor).

Next, I thought, "I must have a bad CHT sensor". I buy a replacement and go through all of the fun involved removing the alternator and remove the old sensor. I decide to test the old and new sensor.

I tested each CHT sensor's resistance readings in
1) a cold cup of water
2) a warm cup of water (~100 degrees F)
3) an almost boiling cup of water (close to 190 degrees F).

Readings from both CHT sensors responded well and were nearly identical. Each reading was within 100 ohms which is expected. I'm about to put my alternator back on and return my car to a running condition tonight. I am not expecting any improved results.

I'm going to make sure that I check a few of the grounds for the wiring harnesses. I can't seem to figure out WHY my focus's ECU is telling me that the Engine Temp is only around 100-130 degrees F if my CHT is behaving as expected. The only logical reason would be a voltage drop in the sensor feed?

Throttle plate adjustment is something not nearly as hard as mentioned. Here's what I do- but only if I know it's out of adjustment. If there is any question, I leave it alone.

I use a pencil with an eraser for this, but you can use a screwdriver- it's just harder to hold still. Back off the adjustment screw until it lifts off because the throttle plate is resting inside the TB. Put the pencil on the throttle plate to sense movement. With the other hand, slowly start screwing the screw down until you feel the throttle plate move. Stop. Start the engine. That should do it. Be very careful adjusting your idle with this screw- that's not what it's for. It's called a throttle plate stop screw, and that's what it's for- to stop the throttle plate so it won't wear out the inside of the TB. Now if this was a carb, then it might be an idle adjustment screw.

So I'm back at square one with the high idle issue. Apparently the dash diagnostics are telling me the engine temp in Celsius even though it clearly has an 'F' in the display!! So the engine is reaching normal temperature, radiator fans work correctly, etc, etc.

I have a scan tool that I can monitor things with. What should I look for? I'm going to verify the voltage range of the tps and some other things.

At this point I might just break down and buy a motorcraft IAC valve. Has anyone had bad luck with IAC valves from autozone? Again, if I disconnect the IAC valve, the car runs great and idles just as you'd expect a car to idle at.

Again, if I disconnect the IAC valve, the car runs great and idles just as you'd expect a car to idle at.

That's a good sign that the IAC is bad. I usually recommend people remove the IAC, and clean it before purchasing a replacement. Afterwards, reset the A/F ratio by first warming the engine up by driving around, then disconnect the battery for 10 mins or so. Reconnect the battery, and start the engine. The idle should go up, then settle around 1k rpm. Allow the engine to idle for 5 mins without touching the accelerator. During this time you might notice slight fluctuations in the idle- that's normal. Once the ECU is done with the A/F test, the idle should settle around 700 rpm. That should fix it- if the IAC is not damaged.

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